[RFC PATCH v2 0/6] drm/gma500: prepare GEM and MMU for 3D rendering and hybrid 2D

[Gabriel Gama <operatingsystemsdepression@gmail.com>]

Hi,

This v2 targets Linux 7.4-rc2 at
7475ea8b58616b33c04afb976cf0fbaad9dd63fb. The six patches improve existing
gma500 GEM and SGX MMU handling as prerequisites for future 3D rendering
and hybrid CPU/GPU 2D. They do not enable either rendering path or add a
userspace ABI. Display GTT and SGX page tables remain separate mappings.

Since v1, I verified the introducing commits for patches 3 and 5 and added
Fixes tags. Patch 6 now handles initialization failure correctly: KUnit
still invokes the per-case exit callback, so partial resources are released
once through a NULL-safe cleanup rather than freed again through stale
pointers. The successful fixture path is unchanged.

Cross-builds and native/UBSan checks ran in Debian AArch64 Linux userspace
under PRoot. The i386 LLVM 19 W=1/HIGHMEM4G kernel linked successfully, and
all nine MMU KUnit cases passed in a QEMU TCG guest. Eleven host allocation
budgets checked fixture init failure and repeated cleanup. Physical Mini12
testing remains pending; no hardware rendering result is claimed.

Changes since v1:
  - Patch 3: Fixes tag for 8c8f1c958ab5.
  - Patch 5: Fixes tag for ae012bdc5799.
  - Patch 6: safe partial-init cleanup, checked with allocation failures.

Patch list:
  1. Use the common dumb-buffer size helper.
  2. Prevent GEM unpin underflow.
  3. Fix SGX page-table cache-flush mapping lifetime.
  4. Make MMU insertion checked and transactional.
  5. Propagate MMU setup and GEM pin failures.
  6. Add software-only MMU KUnit coverage.

Previous version: Message-ID
<20261109055451.17458-1-operatingsystemsdepression@gmail.com>

Thanks,
Gabriel Gama